1. Technical Field
The present disclosure relates to a positive electrode active material for lithium ion secondary battery, a positive electrode for lithium ion secondary battery, and a lithium ion secondary battery using the same.
2. Description of the Related Art
In recent years, lithium ion secondary batteries have attracted attention as a power supply for large devices, such as electric vehicles, as well as for mobile devices. Accordingly, further improvement and increase in the rate characteristics and energy density of the lithium ion secondary batteries are desired. The lithium ion secondary battery typically includes a positive electrode, a negative electrode, an electrolyte, and a separator. Among others, an improvement in rate characteristics can be expected by improving the characteristics of the positive electrode.
For example, JP-A-2007-173134 and JP-T-2014-510997 report techniques for decreasing the internal resistance of the positive electrode by coating the surface of positive electrode active material particles with conductive material. Further, in JP-A-2012-234766, the degree of carbonization (electronic conductivity) of a coating layer is controlled by means of the intensity ratio of a G band and a D band of a Raman spectrum of active material particles including carbon in the surface thereof. In this way, an improvement in rate characteristics can be obtained.
However, as the use of the lithium ion secondary battery become more widespread, a further improvement in rate characteristics is desired.